Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$98.83	12.436%	$111.1205	$111.12	$111.10	$111.10
Purchase #2	$54.43	6.435%	$57.9326	$57.93	$57.95	$57.90
Purchase #3	$234.77	6.249%	$249.4408	$249.44	$249.45	$249.40
Purchase #4	$120.87	10.126%	$133.1093	$133.11	$133.10	$133.10
Purchase #5	$168.94	12.535%	$190.1166	$190.12	$190.10	$190.10
Purchase #6	$217.39	11.253%	$241.8529	$241.85	$241.85	$241.90
Purchase #7	$56.26	6.720%	$60.0407	$60.04	$60.05	$60.00
7 purchase totals =	$951.49		$1,043.6134	$1,043.61	$1,043.60	$1,043.50